1.20. /tmp

This directory contains mostly files that are required temporarily. Many
programs use this to create lock files and for temporary storage of data. Do
not remove files from this directory unless you know exactly what you are doing!
Many of these files are important for currently running programs and deleting
them may result in a system crash. Usually it won't contain more than a few KB
anyway. On most systems, this directory is cleared out at boot or at shutdown
by the local system. The basis for this was historical precedent and common
practice. However, it was not made a requirement because system administration
is not within the scope of the FSSTND. For this reason people and programs must
not assume that any files or directories in /tmp are preserved between
invocations of the program. The reasoning behind this is for compliance with
IEEE standard P1003.2 (POSIX, part 2).